Comparative Studies of Stress-Corrosion Cracking of Long-Term Operated Main Gas Pipeline Pipe and Storage Pipe Made Of X70 Steel

Keywords

pipe steel Х70, long term operation, stress-corrosion cracking, electrolytic hydrogenation, voltammetry, slow strain test method, optical microscopy, SEM

Abstract

The susceptibility to stress-corrosion cracking of the pipe metal of a long-term operated for 40 years main gas pipeline made of X70 steel and an emergency reserve pipe during cathodic protection in NS4 was investigated. A tendency towards some increase in susceptibility to stress corrosion cracking at a potential shift of -0.75 to -1.05 V was found for the serviced pipe compared to stock pipe metal. It is shown that the value of KS is slightly higher for the operated pipe, which indicates the possible embrittlement of the steel with long-term exposure to external cathodic polarization.

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